texi2dvi --tidy somewhat flawed

[Gavin Smith]

If I have the following in test.texi:

\input texinfo

@cindex foo

@printindex cp
@bye

and run texi2dvi test.texi, the index will be output with the foo entry.

Then if I change the file to

\input texinfo

@cindex bar

@printindex cp
@bye

and run texi2dvi --tidy test.texi, texi2dvi will appear to run 
successfully: but the index will still have foo in it, not bar.
The same issue exists for --build-dir and probably --clean as well.

This is because the test.cps file in the same directory as test.texi 
takes precedence over test.t2d/dvi/build/test.cps.

I knocked against this issue when trying to build doc/info-stnd.pdf 
using the Makefile rules, after having previously run texi2pdf manually 
in the doc/ directory.

I doubt that there is any way around this.  Copying the input file to the 
build directory wouldn't work because it may @include other files.

Maybe texi2dvi should delete auxiliary files in the same directory as 
the input file if --build-dir is being used.